First record of natural helminth infection in early larval stages of two Anuran species.

This study reports trematode infection in tadpoles at early developmental stages under natural conditions. While most previous records describe infections in more advanced stages, we identified metacercariae of the diplostomid Neodiplostomum sp. in tadpoles of five anuran species at the Gosner stage between 25 and 28. A total of 207 tadpoles from eight species (Families Hylidae and Leptodactylidae) were collected from seasonal water bodies from Brazil, of which 39 were found parasitized with helminths. Within this group of infected tadpoles, 20 were specifically parasitized by trematodes, 12 of them at the earliest stages of tadpole development (Gosner stage 25). This record indicates that tadpole infection with trematodes may occur earlier than previously documented, providing new insights into the infection dynamics of larval trematodes.